Math Problem Statement

Solve the system of equations: x² + y² = 25 and x² - 4y² = 9.

Solution

To solve the given system of equations for xx and yy:

x^2 + y^2 = 25 \quad \text{(1)}\\ x^2 - 4y^2 = 9 \quad \text{(2)} \end{cases}$$ ### Step-by-Step Solution 1. **Subtract Equation (2) from Equation (1):** $$(x^2 + y^2) - (x^2 - 4y^2) = 25 - 9$$ Simplifying: $$x^2 + y^2 - x^2 + 4y^2 = 16$$ This gives: $$5y^2 = 16$$ Therefore: $$y^2 = \frac{16}{5}$$ 2. **Substitute $$y^2 = \frac{16}{5}$$ into Equation (1):** $$x^2 + y^2 = 25$$ Plugging in $$y^2 = \frac{16}{5}$$: $$x^2 + \frac{16}{5} = 25$$ To clear the fraction, multiply everything by 5: $$5x^2 + 16 = 125$$ Solving for $$x^2$$: $$5x^2 = 109$$ Therefore: $$x^2 = \frac{109}{5}$$ 3. **Find the Values of $$x$$ and $$y$$:** - $$x = \pm \sqrt{\frac{109}{5}}$$ - $$y = \pm \sqrt{\frac{16}{5}}$$ Thus, the solutions are: $$(x, y) = \left( \sqrt{\frac{109}{5}}, \sqrt{\frac{16}{5}} \right), \left( \sqrt{\frac{109}{5}}, -\sqrt{\frac{16}{5}} \right), \left( -\sqrt{\frac{109}{5}}, \sqrt{\frac{16}{5}} \right), \left( -\sqrt{\frac{109}{5}}, -\sqrt{\frac{16}{5}} \right)$$ --- ### Final Solutions: $$\left( \sqrt{\frac{109}{5}}, \sqrt{\frac{16}{5}} \right), \quad \left( \sqrt{\frac{109}{5}}, -\sqrt{\frac{16}{5}} \right), \quad \left( -\sqrt{\frac{109}{5}}, \sqrt{\frac{16}{5}} \right), \quad \left( -\sqrt{\frac{109}{5}}, -\sqrt{\frac{16}{5}} \right)$$ Would you like further details on the steps, or have any questions? --- ### Related Questions 1. How would you solve the system if one of the equations were linear? 2. How do you graph the solutions for these types of systems? 3. What does the intersection of these curves represent geometrically? 4. How would this problem change if the constant in the second equation were different? 5. How can substitution methods help in solving nonlinear systems? ### Tip In solving systems of equations, eliminating one variable often simplifies the problem significantly.

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Math Problem Analysis

Mathematical Concepts

Algebra
Systems of Equations
Quadratic Equations

Formulas

Equation of a circle: x² + y² = r²
Difference of squares: a² - b² = (a - b)(a + b)

Theorems

Methods for solving systems of equations
Substitution and elimination methods

Suitable Grade Level

Grades 10-12